1. Energy Engineering

ME-181

Introduction to Mechanical

Engineering

LEVEL-1, TERM-I

Adib Bin Rashid

Capt

Instructor Class C

Mechanical Engineering Department

Adib Bin Rashid

Capt

Instructor Class C

Mechanical Engineering Department

Energy engineering

Energy engineering or Energy systems is a broad field

of engineering dealing with energy efficiency, energy services, facility

management, plant engineering, environmental compliance and alternative

energy technologies.

Mechanical Energy:

•Defined as energy which can be used to raise a weight.

•Can be easily and efficiently converted into other energy forms.

Electrical Energy:

•Defined as that class of energy associated with the flow oraccumulation of electrons.

•Large quantities of electrical energy are transferred over longdistances with the use of high-voltage transmission lines.

•Can be converted into other energy forms.

Electromagnetic Energy:

•Defined as that form of energy associated with electromagnetic

radiation.

•Extensively employed in nuclear energy study.

Chemical Energy:

•Defined as energy that is released as the result of electron interactions

in which

two or more atoms and/or molecules combine to produce a more stable

chemical compound.

•Commonly reported in the units of energy per unit mass or “mole” of

fuel reactant

Sources of energy :-

There are two main sources of energy. They areconventional and non conventional sources ofenergy.

i) Conventional sources of energy :- are wood,flowing water and fossil fuels (coal, petroleum,natural gas).

ii) Non conventional sources of energy :- are solarenergy, wind energy, biomass energy, ocean energy(tidal energy, wave energy, ocean thermal energy),geothermal energy, nuclear energy etc.

Some sources of energy are renewable like sun, wind,flowing water, ocean, wood, biomass etc.

Some sources of energy are non renewable like coal,petroleum and natural gas.

Conventional sources of

energy :-

Fossil fuels :-are fuels formed inside the earth from the remains of plants and

animals after millions of years. The fossil fuels are coal, petroleumand natural gas. Fossil fuels are non renewable sources of energyso they should be conserved and used judiciously.

Disadvantages of fossil fuels :-

i) Burning of fossil fuels release gases and harmful particles which causes air pollution.

ii) Burning of fossil fuels release acidic oxides of sulphur and nitrogen which causes acid rain which is harmful for living organisms, affects soil and water, causes damage to buildings, corrosion of metals etc.

iii) Burning of fossil fuels release a large amount of carbon dioxide gas which increases the temperature of the atmosphere and causes global warming (green house effect).

Fossil Fuels:

Fossil Fuels are formed from Living things millions of years ago. They are Hydrocarbons and are Finite Fuels ie. They will run out in the future and cannot be regenerated. There are three main Fossil Fuels:

Coal, Oil and Gas

Oil: This was formed by dead sea creaturesfalling to the sea-bed where they were subjected to chemical change by Bacteria.

Coal: This was

formed by the

decay of

Vegetation which

was subjected to

heat and pressure

over a very long

period of time.

Gas was formed

in much the

same way as Oil.

It is often

collected when

drilling for Oil.

Classification of Fuel

Fuels may be classified into the following general terms:

1. Solid Fuel

2. Liquid Fuels

3. Gaseous Fuel

Each of these fuels may be subdivided into the following categories-

1. Natural Fuels

2. Prepared Fuels

Solid Fuel

Wood: At one time it was an extensively used fuel. It consists of mainly carbon and hydrogen.

Peat: It is a spongy humid substance and contains about 30% water. It has to be dried before use. It is the first stage in the formation of coal.

Lignite or brown coal: It is the next stage of peat in the coal formation and an intermediate variety between bituminous coal and peat. It contains nearly 40% moisture and 60% of carbon.

Solid Fuel

Bituminous Coal: It represents the next

stage of lignite in the coal formation and

contains very little moisture(4-6%) and 75 to

90% of carbon.

Anthracite Coal: It represents the final

stage of coal formation and contains 90% or

more carbon.

Solid Fuel

Wood Charcoal: It is made by heating wood

with a limited supply of air to a temperature

not less than 280˚C.

Briquetted Coal: It is produced from finely

ground coal by moulding under pressure

with or without a binding material.

Pulverised Coal: The low grade coal with

high ash content is powdered to produce

pulverised coal.

Coal composition and rank:

All of the fossil fuels are produced from the fossilizationof carbohydrate compounds.

Coal, the most abundant fossil fuel, is thought to befossilized vegetation.

It is estimated that at least 20 ft of compactedvegetation was necessary to produce a 1-ft-thick seamof coal.

This compacted coal is then converted into peat, a low-grade fuel, then into brown, then into lignite, then intosub bituminous coal, then into bituminous coal, andfinally into anthracitic coal.

Aging process progresses, coal becomes harder,hydrogen and oxygen fractions decrease, moisturecontent decreases, and carbon fraction increases.

Coal composition and rank:

Coal is an organic rock (as opposed to most

other rocks in the earth's crust, such as clays

and sandstone, which are inorganic).

It contains mostly carbon (C), but it also has

hydrogen (H), oxygen (O), sulfur (S) and

nitrogen (N), as well as some inorganic

constituents (minerals) and water (H2O).

Coal composition and rank:

It is estimated that at least 20 ft of compacted

vegetation was necessary to produce a 1-ft-thick

seam of coal .

Coal composition and rank: There are several different systems used for classifying coal, but the

American Society for Testing Materials (ASTM) has developed a method for

ranking coal into four major classifications:

Class I Coals: Anthracitic coals

Class II Coals: Bituminous coals

Class III Coals: Sub bituminous coals

Class IV Coals: Lignite coals

Liquid Fuels

Almost all the commercial liquid fuels are derivedfrom natural petroleum. The liquid fuels consist ofhydrocarbons.

The natural petroleum may be separated intopetrol or gasoline, paraffin oil or kerosene, fuel oilsand lubricating oil by boiling the crude oil atdifferent temperature and subsequent fractionaldistillation.

The following liquid fuels are important from thesubjects point of view.

Liquid Fuels

1. Petrol or gasoline: It is the lightest and most volatile liquid fuel, mainly used for light petrol engines. It is distilled at a temperature from 65˚-220˚C.

2. Kerosene or Paraffin oil: It is the heavier and less volatile fuel than the petrol, and is used as heating and lighting fuel. It is distilled from 220˚-345˚C

3. Heavy Fuel oil: The liquid fuels distilled after petrol and kerosene are known as heavy fuel oil. These oils are used in diesel engines and oil fired boilers. They are distilled at a temperature from 345˚-470˚C.

Merits and Demerits of Liquid Fuel

over Solid Fuel Following are the merits and demerits Solid Fuel:

Merits:

1. Higher Calorific value.

2. Lower storage capacity required.

3. Better economy in handling.

4. Better control of consumption by using valves.

5. Practically no ashes.

6. Non-deterioration in storage.

7. Non-corrosion of boiler plants.

8. Higher efficiency.

Merits and Demerits of Liquid Fuel

over Solid Fuel

Demerits:

1. Higher cost

2. Greater risk of fire.

3. Costly containers are required for storage

and transport.

Gaseous Fuel

The natural gas is, usually found in or near the petroleum fields, under the earth’s surface. It essentially consists of marsh gas or methane(CH4) together with small amounts of other gases such as ethane(C2H6), carbon dioxide(CO2).

The following gaseous fuels are important from subject point of view.

1. Coal gas: It is obtained by carbonization of coal and consists mainly of H2,CO and various hydrocarbons.

2. Producer Gas: It is obtained by the partial combustion of coal, coke, anthracite coal or charcoal in a mixed air-steam blast.

Gaseous Fuel

Water gas: It is a mixture of H2 and CO and ismade by passing steam over incandescentcoke.

Mond Gas: It is produced by passing air and alarge amount of steam over waste coal at about650C.

Blast Furnace Gas: It is a by-product in theproduction of pig iron in the blast furnace.

Coke oven gas: It is by-product from cokeoven and is obtained by the carbonization ofbituminous coal.

Merits and Demerits of Gaseous

Fuel:

Merits:

1. The supply of fuel gas and hence the temperature of furnace is easily and accurately controlled.

2. The high temperature is obtained at a moderate cost by pre-heating gas and air with heat of waste gases of combustion.

3. They are directly used in internal combustion engine.

4. They do not produce ash or smoke.

5. They undergo complete combustion with minimum air supply.

Merits and Demerits of Gaseous

Fuel

Demerits:

1. They are readily inflammable.

2. They require large storage capacity.

Requirements of Good Fuel

1. A good fuel should have low ignition point.

2. It should have a high calorific value.

3. It should freely burn with a high efficiency, one it is ignited.

4. It should not produce harmful gases.

5. It should produce least quality of smoke and gases.

6. It should be economical, easy to store and convenient for transportation.

Thermal power plants :-

In thermal power plants the heat energy

produced by burning fossil fuels like coal,

petroleum or natural gas is used to heat

water and change it into steam which

rotates the turbines of generators to

produce electricity.

Thermal power plants :-

Thermal power plants :-

Thermal power plants :-

Hydro power plants :-

In hydro power plants water from rivers are

stored by constructing dams. The water

from the dam flows down through pipes and

rotates the turbines of generators to

produce electricity.

Hydro power plants :-

Hydro power plants :-

Hydro power plants :- Advantages :-

i) Flowing water is a renewable source of energy.

ii) The electricity produced does not cause pollution.

iii) The water stored in dams can also be used to control floodsand for irrigation.

Disadvantages :-

i) The initial cost is high.

ii) Large areas of land gets submerged and the decompositionof vegetation produces methane gas which is a green housegas.

iii) It causes displacement of people from large areas of land.

Non conventional sources of

Energy :-

Non conventional sources of

Energy :-Biomass energy :-

The waste materials and dead parts of living things are

called biomass. Eg :- wood, animal dung, vegetable

waste, agricultural waste, sewage etc. Biomass is

decomposed by anaerobic microorganisms to produce

biogas.

Biogas is a mixture of gases containing methane, carbon

dioxide, hydrogen and hydrogen sulphide.

Biogas plant :-

The biogas plant has a large underground tank made of

bricks and cement. The lower part is the digester and

the upper part has a dome with a gas outlet. On one side

of the tank above the ground is a mixing tank and on

the other side is an overflow tank. Animal dung is

mixed with water in the mixing tank and the slurry is

sent into the digester. In the digester the slurry is

decomposed by anaerobic microorganisms and after a

few days biogas is produced. The gas is taken out

through the gas outlet and used for heating and lighting

purposes. The slurry left behind is rich in nitrogen and

phosphorus and is used as manure for crops.

FIXED DOME TYPE BIOGAS

PLANT

Wind energy :-Wind energy is used in wind mills which converts the kinetic

energy of the wind into mechanical or electrical energy. Thekinetic energy of wind can be used to do mechanical worklike lifting water from wells or grinding grains in flour mills. Itcan also be used to rotate the turbines of generators toproduce electricity.

A single wind mill produces only a small amount of electricity.So a large number of wind mills in a large area are coupledtogether to produce more electricity in wind energy farms.

Advantages :-

i) It is a renewable source of energy.

ii) It does not cause pollution.

iii) The recurring cost is less.

Disadvantages :-

i) Wind is not available at all times.

ii) It requires a large area of land.

iii) A minimum wind speed of 15 km/h is required

Solar energy :-Solar energy is the energy obtained from the sun in the form of heat and light. The heat

energy is used in solar heating devices like solar cooker, solar water heater, solar

furnaces etc. The light energy is used in solar cells.

i) Solar cooker :- The box type solar cooker has an insulated box painted black

inside. It is covered by a glass plate which allows heat to enter inside but does not

allow heat to escape out. It has a mirror to reflect more sunlight into the box. The

food to be cooked is kept in containers inside the box It can produce a

temperature of 100° to 140°.

Solar energy :-

ii) Solar water heater :- A solar water heater has an insulated box painted black

inside with a system of copper tubes. It is covered with a glass plate which allows

heat to enter inside but does not allow heat to escape out. When water flows

through the copper tube it absorbs heat and becomes hot

Solar cells :-Solar cell is a device which converts solar energy into electrical

energy. Solar cells are made from semi conductors like silicon,germanium, gallium etc. A single solar cell produces a voltage ofabout 0.5 to 1 V and produces about 0.7 W electricity. So severalsolar cells are arranged in a solar panel to produce more electricity.

Solar cells :-

Advantages :-

i) It uses renewable source of energy.

ii) It produces electricity which does not cause pollution.

iii) It can be used in remote areas where there is no power supply.

Disadvantages :-

i) It uses a special grade of silicon which is expensive.

ii) Since silver is used for connecting the cells together it is more

expensive.

iii) The current produced is DC and to convert it to AC increases the cost.

Energy from the sea :-Energy from the sea is obtained in three different forms. They are Tidal energy,

Sea wave energy and Ocean thermal energy.

i) Tidal energy :-

The periodic rise and fall of sea level due to gravitational attraction of the moon

causes tides. A dam is constructed at a narrow opening between the land and

sea. The movement of water during high tide and low tide can be used to

rotate the turbines of generators to produce electricity.

Energy from the sea :-

ii) Sea wave energy :-

When strong wind blows over the sea it produces huge waves. The kinetic energy

of the moving waves can be used to rotate the turbines of generators to

produce electricity.

Energy from the sea :-iii) Ocean thermal energy :-

There is a temperature difference between the warm surface water and the cold

water at the bottom of the oceans. This difference is about 20°C. The warm

surface water is used to boil liquid ammonia and the vapour is used to rotate the

turbines of generators to produce electricity. The cold water from the bottom is

then pumped up to cool the vapour back to liquid

Geothermal energy :- The deeper regions of the earth’s crust is very hot. This heat melts

rocks and forms magma. The magma moves up and collects below at

some places called Hot spots. The underground water in contact with

hot spot gets heated into steam at high pressure. By drilling holes

into hot spots the steam coming out can be used to rotate turbines of

generators to produce electricity.

Nuclear energy :-

Nuclear energy is the energy is the energy released

during nuclear reactions. During nuclear reactions

some mass is converted into energy and so a very

large amount of energy is produced during nuclear

reactions. Nuclear reactions are of two types. They

are Nuclear fission and nuclear fusion

Nuclear energy :-i) Nuclear fission :-

is a nuclear reaction in which the nucleus of a heavy atom like

uranium, plutonium, etc. splits into smaller nuclei with the

release of a large amount of energy. It is used to make atom

bombs and to produce electricity. In a nuclear power plant the

heat energy produced by a controlled nuclear fission chain

reaction is used to produce steam which rotates the turbines of

generators to produce electricity.

Nuclear energy :-

ii) Nuclear fusion :-

is a nuclear reaction in which small nuclei fuse

together to form a heavier nucleus with the release of

a very large amount of energy. The energy of sun is

produced by the fusion of hydrogen nuclei to form

helium nucleus. It is also used to make the hydrogen

bomb.

Nuclear energy :-

Advantages of nuclear energy :-

i) It produces a very large amount of energy per unit mass

than any other source of energy.

ii) If safety measures are taken, it is more environment

friendly than fossil fuels.

Disadvantages of nuclear energy :-i) The cost of a nuclear reactor is very high.

ii) The availability of nuclear fuel is limited.

iii) Nuclear reactors produce harmful nuclear wastes which is

difficult to dispose.

Nuclear Power Plant